Certain processes for producing 2-chloropyridine-N-oxide from 2-chloropyridine are well known. Illustrative prior art processes relate to the oxidation of 2-chloropyridine with hydrogen peroxide in the presence of homogeneous catalysts(s), such as tungstates, molybdates, and the like. As another illustration, U.S. Pat. No. 3,047,579 discloses soluble peroxy carboxylic acid catalysts for use in the preparation of N-oxides of tertiary organic bases, including halo-pyridine N-oxides.
The use of homogeneous catalysts for the oxidation of 2-chloropyridine, and other pyridine compounds, has the attendant disadvantage that the catalyst must be removed from the product stream and then recovered in reusable form. To achieve this recovery and reusability requires a number of steps, such as precipitation of the catalyst, filtration to separate the precipitated catalyst from the filtrate, and then reconversion of the precipitate back to its original catalytic form. These steps add considerably to the cost of producing the desired 2-chloropyridine-N-oxide product.
There are other costs and additional process complexities that make the use of soluble catalysts in homogeneous systems even more disadvantageous. For example, in such systems, the reaction is typically stopped using a quenching agent. The reaction between the soluble catalyst(s) and the quenching agent typically results in the formation of an insoluble product which is then typically removed by filtration using a filter aid.
Unfortunately, the use of the quenching agent and/or the filter aid increase the likelihood of introducing undesirable impurities into the desired 2-chloropyridine-N-oxide product. Accordingly, new processes for producing 2-chloropyridine-N-oxide that do not use a homogeneous catalyst system, do not employ a quenching agent, do not employ filter aid(s), and employ fewer process steps than prior art processes employing soluble catalysts, would be highly desired by, for example, the biocides intermediates manufacturing community. The present invention provides one such process.